Thermal stability and microstructure of germanium antimony telluride thin films under interdiffusion conditions

This paper investigates the interdiffusion behaviors of alloy components of the Ge-Sb-Te system and its influence on the thermal and electrical instability of Ge-Sb-Te alloy films. When SbxTe1−x/Ge bilayer films are annealed at 400 °C, the Ge-Sb-Te intermediate layers are formed at the interface between SbxTe1−x and Ge. This is caused by the interdiffusion of Ge, Sb, and Te. The highest degree of interdiffusion is observed in the Ge-Te system, while the existence of Sb retards the interdiffusion of Ge and Te in the SbxTe1−x/Ge bilayer films. The outdiffusion and sublimation of low-melting-point Sb and Te occur at the annealing temperature of 500 °C, which leads to the instability of the Ge-Sb-Te intermediate layers. The phase-change memory (PCM) device employing a Ge2Sb2Te5 intermediate layer exhibit stable endurance, because of the robustness of Ge2Sb2Te5 compound with respect to the phase separation during the repetitive set-reset cycles.